CN110333225B - Preparation method of cubic nanogold SERS (surface enhanced Raman scattering) probe for TNT (trinitrotoluene) detection - Google Patents

Preparation method of cubic nanogold SERS (surface enhanced Raman scattering) probe for TNT (trinitrotoluene) detection Download PDF

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CN110333225B
CN110333225B CN201910692866.6A CN201910692866A CN110333225B CN 110333225 B CN110333225 B CN 110333225B CN 201910692866 A CN201910692866 A CN 201910692866A CN 110333225 B CN110333225 B CN 110333225B
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高大明
张立东
陈倩云
朱德春
陈红
张宇刚
张慧
张凌云
刘安求
王晓晨
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Abstract

A preparation method of a cubic nanogold SERS probe for TNT detection comprises the steps of seed gold preparation, further growth, functional modification and self-assembly of a silicon chip. The preparation process comprises the following steps: firstly, preparing seed gold and further growing, secondly, strictly controlling the growth environment through a seed growth mechanism to enable the seed gold to grow into a cubic structure, and then, grinding the seed gold by 1 multiplied by 1cm2Modifying sulfydryl on a silicon wafer to enable gold particles to be self-assembled on the surface of the silicon wafer in a single layer, finally modifying amino rich in electrons on the surface of the silicon wafer, further performing electrostatic interaction with three electron-deficient nitro groups in TNT target molecules to realize selective recognition of TNT, amplifying and enhancing conventional Raman signals of the TNT molecules by utilizing a local plasma resonance field on the surface of nano gold, realizing trace detection of the TNT, wherein the detection limit is 10‑ 9mol·L‑1. The invention has the advantages of simple preparation, convenient operation, low cost, good selectivity and high sensitivity.

Description

Preparation method of cubic nanogold SERS (surface enhanced Raman scattering) probe for TNT (trinitrotoluene) detection
Technical Field
The invention relates to the field of material science, in particular to a preparation method of a cubic nanogold SERS (surface enhanced Raman scattering) probe for TNT (trinitrotoluene) detection.
Background
Trinitrotoluene (TNT) is a military explosive with the widest application range, and is widely used in blasting industries such as civil use, mines and the like, TNT has a strong explosion risk and poses an important threat to environmental safety, TNT is often left in natural environment in production, manufacture and transportation, soil and water environments are polluted due to biological persistence, toxicity and mutagenicity, people can cause irreversible damage to life health after drinking water polluted by TNT directly or indirectly, besides causing wide damage, harmful substances derived from explosives can be accumulated in the environment for a long time in the processes of using, treating, storing and dumping, and TNT is proved to cause anemia, liver dysfunction and carcinogenesis at present, so that the development of a detection method with high selectivity, high sensitivity and trace amount on TNT is particularly important.
At present, the increase of national safety and public safety awareness increases the wide interest of people in developing selective, sensitive and rapid detection of nitroaromatic explosives, and many techniques for detecting TNT, such as solid-phase microextraction, have advantages over traditional extraction methods, especially when analyzing small amounts of gaseous substances. Sample preparation is very convenient because no additional solvent is required and extraction can be performed in the sample or in the headspace above the sample using fused silica fibers coated with an adsorbent material. Interference of impurities in the sample matrix can be minimized by headspace sampling, with the extracted compounds pyrolyzed from the fibers and directed to the interface of the chromatography system for detection and analysis. Furton KG et al have successfully applied this technique to the recovery of explosives (J. Chromatogr. A2000, 885, 419-432), Jonsson S et al further use for the detection of explosives (S) ((r)J. Chromatogr. A,2007, 1164, 65-73.). However, this method has drawbacks and deficiencies in sensitivity, selectivity, speed, versatility and dynamic range. Another method for detecting explosives is gas chromatography, gas phaseThe separation in chromatography takes place in a column between a mobile phase and a stationary phase, consisting of a gas stream containing the separated target substance, each eluting substance producing a characteristic retention time signal which can be further used for data analysis. Bowerbank CR et al successfully used gas chromatography to detect explosives (J. Chromatogr. A2000, 902, 413-419.), but other compounds with similar explosive properties, including negatively charged halides, organosulfur or organophosphorous compounds, may interfere with elution and pyrolysis. In addition, liquid chromatography is also used for the detection of explosives, where a liquid sample is injected into a liquid mobile phase stream to pass through a column containing a solid stationary phase, and a target compound is separated between the mobile phase and the stationary phase. Monteil-river F et al used this method to detect explosives in water samples: (J. Chromatogr. A2004, 1048, 213- & 221.), but the samples typically require sonication, extraction and pre-concentration prior to analysis. In addition, due to the redox property of the nitro explosives, namely the property that the nitro is easily reduced, the electrochemical detection is facilitated, so that the electrochemical method is changed in the detection of the explosives, including in a mercury membrane electrode (Anal. Chim. Acta，1981，130，295-311；Talanta，2002，58，919-926；Talanta2006, 69, 984-Talanta，2006，69，656-662；Electroanalysis2012, 24, 1811-Anal. Chim. Acta，2003，485，139-144；Sensors and Actuators B: Chemical，2005，106，296-301；Electroanalysis2006, 18, 971-975.) that, while capable of detection purposes, are highly dependent and time consuming, and therefore, are difficult to apply to on-site and real-time detection of explosives. To this end, many researchers have developed various simple luminescence chemosensors for TNT detection ((r))Anal. Chem.，2008，80，8545-8553；Trends Anal. Chem.，2014，62，123-134；Anal. Chim. Acta.，2013，802，89-94；Nature Comm.，2015，6，1-7；US20040101900A 1) and an immunoassay for the specific detection of TNT based on fluorescence resonance energy transfer by binding luminescent quantum dots to antibody fragments: (J. Am. Chem. Soc.,2005, 127, 6744-6751.). Although these methods have high sensitivity, the synthesis is difficult to control, and the methods are too cumbersome, the obtained effect is not ideal, the background value is limited greatly, and the applicability of field detection is still limited. In conclusion, although the method can realize the detection of TNT to a certain extent, the method has corresponding limitations in the aspects of selectivity, sensitivity, size and cost, so that the trace detection method with higher sensitivity and higher rapidness and accuracy is urgently needed to be developed.
SERS is the result of interaction between light and matter, and this phenomenon of surface-enhanced raman scattering has been mentioned to date in a variety of theories, where surface plasmons, particularly gold, silver, and copper, in heavy metal nanoparticles can be directly excited by electromagnetic radiation that propagates freely in the visible region, creating a strong electromagnetic field around the nanostructure. When two or more plasmonic nanostructures are placed in close proximity, the spectral signal is significantly enhanced, and since the large enhancement effect provided by the rough nanoscale material surface, such spectroscopy techniques have not been limited to strongly scattering targets or high concentration systems, the oscillating electric field junctions of the plasmonic nanostructures have an amplified electric field called hot spots, well-organized plasmonic structure arrays can produce multiple hot spots, and by immobilizing the molecules at or near the specific nanomaterial surface, the raman signal trapped at the hot spot molecules shows a significant enhancement compared to molecules bound at the surface of isolated particles, due to resonances within the molecules themselves or charge transfer between the molecules and the conduction band of the metal substrate, and the presence of electromagnetic effects originating from surface plasmon resonances in the metal substrate. This has led to a wide interest in the field of physical chemistry, and among the various spectroscopic techniques, raman spectroscopy is considered to be an important tool for the rapid identification and quantification of a variety of biological and environmental molecules. This is primarily because raman spectroscopy can be viewed as a fingerprint region of molecular spectroscopy, and the unique but weak raman scattering produced by molecular vibration or relaxation can be used to identify and characterize molecules and is proposed as a SERS substrate for the detection and quantification of various analytes.
In recent years, by virtue of excellent local surface plasmon resonance effect, heavy metals such as gold and silver are widely applied to the research of SERS substrates, as is well known, SERS has the characteristics of low cost, simple operation, good mobility, high sensitivity, good selectivity, fingerprint spectrum and the like, is widely applied to the fields of surface science, material science, biomedicine, drug analysis, food safety, environmental detection and the like, is a trace analysis technology with great potential, and plays a positive role in the detection of explosives, and the like, and the invention patent (CN 102183503A) "a light irradiation preparation method of a surface-enhanced Raman scattering active substrate" is disclosed by Yankee, et al 2011. The specific implementation steps are that silver nanoparticles are firstly deposited on the surface of DNA, and then silver is used as a nucleation site to assemble gold on the silver. Subsequently, the small gold particles are deposited onto the silver-DNA nanostructures again using sunlight. The silver core gold shell or silver-gold alloy nano DNA network structure is used as a surface enhanced Raman scattering active substrate, and TNT detection is realized. Liuhonglin et al discloses an invention patent (CN 103091300A) in 2013, "a TNT detection method based on surface enhanced resonance Raman spectroscopy", which provides a novel SERS-based TNT detection method, firstly synthesizing silver nanoparticles as an SERS substrate and sulfonating and sensitizing TNT, specifically implementing the steps of heating and refluxing a silver nitrate solution with the mass concentration of 100mL of the substance being 1mM to boiling, then adding a sodium citrate solution with the volume of 4mL and the mass fraction being 1% to the silver nanoparticles, boiling for 1 hour to obtain the silver nanoparticles, taking the silver nanoparticles as the SERS substrate for later use, then mixing 1mL of a TNT aqueous solution with the mass concentration of 0.1mM with 1mL of a sulfonation reagent sodium sulfite solution with the mass concentration of 0.1M to ensure that TNT is completely sulfonated, then mixing the sulfonated TNT solution with 1mL of a chlorohexadecylpyridine solution with the mass concentration of 0.1M to sulfonate and sensitizing the TNT, finally, 10 mu L of the mixed solution obtained in the step (2) is uniformly dripped intoAnd (2) obtaining an SERS characteristic fingerprint signal of the TNT on the silicon chip with the silver nanoparticles obtained in the step (1) as a substrate, and realizing the selective detection of the trace TNT. Samuel P et al disclose invention patent (US 08932384B 1) "Surface enhanced Raman spectra substrates for detection of 2,4, 6-trinitrotoluene and 3, 5-dinitro-4-methyllbenzoic acid applications" in 2015, which firstly synthesizes gold sol seeds, and then obtains SERS substrate through further growth and self-assembly, and the specific implementation method is as follows: firstly, 0.1M HAuCl is added4·3H2Aqueous O250 uL was added to 7.5mL of 0.1M CTAB solution, followed by 0.01M NaBH4600uL to obtain gold sol seed, and further processing in AgNO3And adding gold sol seeds into CTAB and ascorbic acid, and further growing the gold sol seeds into a rod-shaped structure, wherein the structure has an SERS effect on explosives. 2016 discloses a invention patent (CN 104297224B) "SERS substrate material and a hotspot excitation method and a characterization thereof," a surface structure capable of generating a hotspot with an enhanced Raman effect is obtained by a method of evaporating Ag after a ZnO nanorod array grows in situ on a galvanized silicon wafer, then the hotspot with the enhanced Raman effect is excited by a specific solvent and the surface structure effect thereof, the specific implementation steps are that firstly, a cleaned silicon wafer is cut into strips, the silicon wafer put in the strips is evaporated by a magnetron sputtering instrument with metal zinc with the purity of 99.99 percent as a target material to obtain the galvanized silicon wafer, and the silicon wafer is immersed in a mixed solution of zinc nitrate and hexamethyltetramine and then put in the magnetron sputtering instrument for plating silver to obtain the required material. The invention patent (CN 107144557A) discloses a silicon-based SERS chip, a preparation method thereof and a TNT detection method, which is invented by He and others in 2017. The silicon wafer with Si-H bond on the surface is reduced in the environment of silver particles to obtain a silicon wafer modified by nano silver, and then the silicon wafer is reacted with a modifying compound capable of reacting with TNT to obtain the silicon-based chip. In 2018, Li Jianfeng et al discloses an invention patent (CN 108827941A) "a method for rapidly detecting TNT in water based on surface-enhanced Raman spectroscopy", the method realizes the detection of TNT by synthesizing gold nanoparticles and then modifying TNT molecules, and concretely relates to the method for detecting TNTThe implementation method comprises the steps of boiling 200mL of chloroauric acid solution with the mass percentage concentration of 0.01%, adding 1.5mL of sodium citrate solution with the volume percentage concentration of 1%, keeping boiling for 30min after the solution turns into reddish brown to obtain gold nanoparticles, performing Meisenheimer complex reaction between TNT and a modifier, namely, strong donor-acceptor interaction exists between amino serving as a ligand and an electron-deficient aromatic ring, and detecting the Meisenheimer complex through the enhancement effect of the nanoparticle sol to realize TNT detection in water.
Although the SERS substrate can detect TNT, there is a need for improvement, and many existing technologies using nanomaterials in sensor manufacturing have difficulty in controlling the material growth, particle size or material structure, and the appearance, size and the like of metal nanoparticles are closely related to the optical properties thereof, such as nanospheres, nanorods and the like, and due to local charge polarization effect, a plurality of absorption peaks are generated in the near infrared region, and how to control the appearance and size of the metal nanoparticles becomes a large factor for promoting SERS. In summary, there is a need to find a nanostructure with simple preparation process, good reproducibility, high selectivity and high sensitivity as a SERS substrate, and the invention creatively prepares a cubic nanogold SERS probe for TNT detection.
The gold nanoparticles have larger extinction wavelength in visible light and near infrared regions, so that the gold nanoparticles have a better SERS effect than other heavy metals, the cubic nanogold can greatly enhance the electromagnetic force on the surfaces and the interiors of the particles, and a part of photons are subjected to inelastic attenuation through the complex local plasma effect of the cubic nanogold particles, so that the wavelength of the photons is changed. In the invention, the single-layer self-assembly of the prepared cubic nanogold on the surface of a mercapto silicon chip modified on the surface is reported based on the surface enhanced Raman principle, and then the surface amino of the silicon chip is subjected to functional modification to obtain the nanogold SERS probe for TNT detection, so that the high-selectivity and high-sensitivity trace detection on TNT is realized.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the defects existing in the prior art, the invention prepares the cubic nanogold SERS probe for trace detection on the TNT on the silicon wafer with the surface modified with the functional group, wherein the TNT is high in selectivity and sensitivity. Firstly, synthesizing gold sol seed crystals by a sodium citrate reduction chloroauric acid method, then growing the seed crystals in the presence of hydroxyl ammonia hydrochloride and silver nitrate to obtain cubic nanogold, then finishing single-layer self-assembly of the cubic nanogold on a silicon wafer with a surface modified with sulfydryl to form a compact and ordered array, and finally modifying aminopropyl on the surface of the silicon wafer to obtain a nanogold SERS probe with a TNT detection function, so that the cubic nanogold SERS probe with a higher selectivity and high sensitivity detection function on TNT is realized.
The technical scheme of the invention is as follows: a preparation method of a cubic nanogold SERS probe for TNT detection is characterized by comprising the following steps: the SERS probe is self-assembled on a silicon chip with a surface modified sulfydryl through cubic gold nanoparticles, amino on the surface of the silicon chip is functionally modified, so that electron-rich amino on the surface of the silicon chip and three electron-poor nitro groups in TNT molecules are subjected to electrostatic interaction, the TNT molecules are adhered to the surface of the square gold nanoparticles, the conventional Raman signal of the TNT molecules is amplified and enhanced by utilizing a local surface plasmon resonance field of the cubic gold nanoparticles, and the TNT detection is realized, and the preparation process of the SERS probe comprises the following three steps:
the first step is the preparation of seed gold sol: firstly, measuring 1-15 mL of HAuCl4Adding the solution into a 250mL three-neck flask containing 50mL deionized water, then placing the solution into a constant-temperature oil bath tank with a reflux device, magnetically stirring at the rotation speed of 400-600 rpm, heating to the temperature of 150-170 ℃, then adding 3-5 mL of a reducing agent A, changing the color of the reaction mixed solution from light yellow to orange, finally changing to wine red, stopping heating and stirring, cooling to room temperature, standing in a dark place, and storing in a refrigerator;
the second step is the preparation of cubic nano-gold particles: firstly, measuring 0.2-1.0 mL HAuCl4Placing the solution and 0.2-1.0 mL of reducing agent B in a 50mL three-mouth beakerPlacing the three-mouth flask in a reciprocating oscillator, oscillating for 5-10 min at a rotation speed of 250-350 rpm, diluting the mixed solution to 10mL by using a stabilizer, continuously oscillating for 9-11 min to fully mix the mixed solution, then adding 0.2-1 mL of a reducing agent C into the mixed solution, then injecting 100uL of the seed gold sol synthesized in the first step by using a microsyringe with the dosage range of 100-1000 uL, then oscillating for 2-6 h at room temperature of 240-260 rpm, placing 2mL of the reaction mixture into a 15mL centrifuge tube, centrifuging for 10min at 7000-9000 rpm, removing supernatant, repeating the steps for 5 times in order to improve the concentration of gold particles in the 15mL centrifuge tube, and re-dispersing the obtained deposited sol in a volume ratio of 1: 1, preparing a mixed solution of 10mL of ethanol and water to obtain cubic nano gold sol;
the third step is the preparation of a cubic nanogold SERS probe: first, 1X 1cm was sanded with 3000 mesh sandpaper2Ultrasonically washing a silicon wafer for 4-6 min by using concentrated sulfuric acid-hydrogen peroxide mixed solution, acetone and deionized water in a volume ratio of 1:4 respectively, standing for 1-3 weeks, slowly oxidizing the surface of the silicon wafer, putting the polished surface of the silicon wafer upwards into ethanol solution containing a binder, adding 100 mu L of catalyst, standing for reaction for 11-13 h, then taking out the silicon wafer, repeatedly washing the silicon wafer with absolute ethyl alcohol, naturally drying the silicon wafer, putting the polished surface of the silicon wafer upwards into a cubic nano-gold sol solution, standing for about 5-7 hours, forming self-assembled nano gold array on the surface of the silicon chip, finally placing the silicon chip into ethanol solution containing functional monomers, and adding 100 mu L of catalyst, standing and reacting for 11-13 h to prepare the cubic nanogold self-assembled array with amino groups on the surface of the silicon wafer, wherein the array has a function of detecting the TNT SERS probe.
As a further improvement to the prior art, in the preparation of the cubic nanogold SERS probe, reducing agents A, B and C are respectively one of silver nitrate, hydroxylamine hydrochloride, sodium borohydride, lithium aluminum hydride, sodium citrate and potassium borohydride, and the method optimally selects the reducing agent A as the sodium citrate, the reducing agent B as the hydroxylamine hydrochloride and the reducing agent C as the silver nitrate; the stabilizer in the preparation of the cubic nanogold SERS probe is a polyethylene glycol 2000 aqueous solution with the mass concentration of 20%; the adhesive in the preparation of the cubic nanogold SERS probe is 3-mercaptopropyltriethoxysilane; the functional monomer in the preparation of the cubic nanogold SERS probe is 3-aminopropyl triethoxysilane; the size of the cubic nanogold in the preparation of the cubic nanogold SERS probe can be controlled by the amount of reactants and the reaction time; the self-assembly structure in the preparation of the cubic nanogold SERS probe is single-layer cubic nanogold with a space structure.
Advantageous effects with respect to the prior art
In recent years, by virtue of excellent local surface plasmon resonance effect, heavy metals such as gold and silver are widely applied to the research of SERS substrates, as is well known, SERS has the characteristics of low cost, simple operation, good mobility, high sensitivity, good selectivity, fingerprint spectrum and the like, is widely applied to the fields of surface science, material science, biomedicine, drug analysis, food safety, environmental detection and the like, is a trace analysis technology with great potential, and plays a positive role in the detection of explosives, and the like, and the invention patent (CN 102183503A) "a light irradiation preparation method of a surface-enhanced Raman scattering active substrate" is disclosed by Yankee, et al 2011. The specific implementation steps are as follows: firstly, silver nanoparticles are deposited on the surface of DNA, then, silver is used as a nucleation site to assemble gold on the silver, and then, sunlight is used again to deposit small gold particles on a silver-DNA nanostructure, and the silver core gold shell or silver-gold alloy nano DNA network structure is used as a surface enhanced Raman scattering active substrate, so that the TNT detection is realized. Liuhong Lin et al in 2013 discloses an invention patent (CN 103091300A) "a TNT detection method based on surface enhanced resonance Raman spectroscopy", the invention provides a novel TNT detection method based on SERS, firstly, silver nanoparticles are synthesized to be used as an SERS substrate, and sulfonation and sensitization are carried out on TNT, and the specific implementation steps are as follows: heating 100mL of 1mM silver nitrate solution to reflux to boiling, adding 4mL of 1% sodium citrate solution, and boiling for 1 hr to obtain the final productAnd (2) taking the silver nanoparticles as an SERS substrate for standby application, mixing 1mL of TNT aqueous solution with the substance concentration of 0.1mM with 1mL of sodium sulfite solution of a sulfonation reagent with the substance concentration of 0.1M to ensure that TNT is completely sulfonated, mixing the sulfonated TNT solution with 1mL of chlorohexadecylpyridine solution with the substance concentration of 0.1M to sulfonate and sensitize the TNT, and finally taking 10 mu L of the mixed solution obtained in the step (2) to uniformly drop the mixed solution on a silicon wafer taking the silver nanoparticles obtained in the step (1) as the substrate to obtain an SERRS characteristic fingerprint signal of the TNT, so that the selective detection of trace TNT can be realized. Samuel P et al disclose invention patent (US 08932384B 1) "Surface enhanced raman spectra substrates for detection of 2,4, 6-trinitroulene and 3, 5-dino-4-methyllbenzoic acid applications" in 2015, which first synthesizes gold sol seeds, and then obtains SERS substrate through further growth and self-assembly, the specific implementation method is: firstly, 0.1M HAuCl is added4·3H2Aqueous O250 uL was added to 7.5mL of 0.1M CTAB solution, followed by 0.01M NaBH4600uL to obtain gold sol seed, and further processing in AgNO3And adding gold sol seeds into CTAB and ascorbic acid, and further growing the gold sol seeds into a rod-shaped structure, wherein the structure has an SERS effect on explosives. 2016 et al disclose a invention patent (CN 104297224B) "SERS substrate material and its hot spot excitation method and characterization", which is obtained by in-situ growing ZnO nanorod array on a galvanized silicon wafer and then evaporating Ag, and then exciting a hot spot with enhanced raman effect by specific solvent and its surface structure effect, and the specific implementation steps are: firstly, cutting a cleaned silicon wafer into strips, evaporating the silicon wafer placed in the strips by using a magnetron sputtering instrument and using metal zinc with the purity of 99.99% as a target material to obtain a galvanized silicon wafer, immersing the silicon wafer into a mixed solution of zinc nitrate and hexamethylenetetramine, taking out the silicon wafer, and placing the silicon wafer into the magnetron sputtering instrument again for silver plating to obtain the required material. Ohio, 2017, Heyao, et al disclose an invention patent (CN 107144557A) "A silicon-based SERS chip, a preparation method thereof and a TNT detection method", which comprises the steps of placing a silicon wafer with Si-H bonds on the surface thereofAnd carrying out reduction reaction in the environment of silver particles to obtain a silicon wafer modified by nano silver, and then reacting with a modification compound capable of reacting with TNT to obtain the silicon-based chip. In 2018, lipjianfeng et al (CN 108827941A) "a method for rapidly detecting TNT in water based on surface-enhanced raman spectroscopy", which synthesizes gold nanoparticles, and then modifies TNT molecules to realize the detection of TNT, and the specific implementation method is that 200mL of chloroauric acid solution with the mass percentage concentration of 0.01% is boiled, 1.5mL of sodium citrate solution with the volume percentage concentration of 1% is added, the solution is changed into reddish brown and kept boiled for 30min to obtain gold nanoparticles, and then Meisenheimer complexation reaction between TNT and a modifier is utilized, that is, a strong donor-acceptor interaction exists between an amino group for supplying electrons as a ligand and an aromatic ring for lacking electrons, and the Meisenheimer complex is detected through the enhancement effect of nanoparticle sol, so that the TNT detection in water is realized.
Although the SERS substrate can realize the detection of TNT, the SERS substrate has many defects, such as poor selectivity, low sensitivity, complex detection and the like. The appearance, size and the like of the metal nanoparticles are closely related to the optical properties of the metal nanoparticles, such as nanospheres, nanorods and the like, and due to the local charge polarization effect, the metal nanoparticles generate a plurality of absorption peaks in a near infrared region, and how to control the appearance and size of the metal nanoparticles becomes a large factor for promoting SERS. In summary, there is a need to find a gold nanostructure with simple preparation process, good reproducibility, high selectivity and high sensitivity as a surface raman enhancement substrate, and the invention creatively prepares a cubic gold nanostructure SERS probe for TNT detection.
The invention firstly prepares the seed gold sol: measuring 1-15 mL HAuCl4Adding the solution into a 250mL three-neck flask containing 50mL deionized water, then placing the solution into a constant-temperature oil bath tank with a reflux device, magnetically stirring at the rotating speed of 400-600 rpm, heating to the temperature of 150-170 ℃, then adding 3-5 mL of a reducing agent A, changing the color of the reaction mixed solution from light yellow to orange, finally changing to wine red, stopping heating, andstirring, cooling to room temperature, standing in a refrigerator in a dark place, and storing;
secondly, preparing cubic gold nanoparticles: measuring 0.2-1.0 mL HAuCl4Placing the solution and 0.2-1.0 mL of reducing agent B in a 50mL three-mouth beaker, placing the three-mouth flask in a reciprocating oscillator, oscillating for 5-10 min at the rotation speed of 250-350 rpm, then diluting the mixed solution to 10mL by using a stabilizing agent, continuing oscillating for 9-11 min to fully mix the mixed solution, then adding 0.2-1 mL of reducing agent C into the mixed solution, then injecting 100-1000 muL of the micro-injector into 100 muL of the seed gold sol synthesized in the first step, then oscillating for 2-6 h at the room temperature of 240-260 rpm, placing 2mL of the reaction mixture in a 15mL centrifuge tube, centrifuging for 10min at 7000-9000 rpm, removing the supernatant, repeating the steps for 5 times in order to improve the concentration of the gold particles in the 15mL centrifuge tube, the resulting precipitated sol was redispersed in a solvent at a volume ratio of 1: 1, preparing a mixed solution of 10mL of ethanol and water to obtain cubic nano gold sol;
and finally, preparing a cubic nanogold SERS probe: will be sanded with 3000 mesh sandpaper to 1X 1cm2Ultrasonically washing a silicon wafer for 4-6 min by using concentrated sulfuric acid-hydrogen peroxide mixed solution, acetone and deionized water in a volume ratio of 1:4 respectively, standing for 1-3 weeks, slowly oxidizing the surface of the silicon wafer, putting the polished surface of the silicon wafer upwards into ethanol solution containing a binder, adding 100 mu L of catalyst, standing for reaction for 11-13 h, then taking out the silicon wafer, repeatedly washing the silicon wafer with absolute ethyl alcohol, naturally drying the silicon wafer, putting the polished surface of the silicon wafer upwards into a cubic nano-gold sol solution, standing for about 5-7 hours, forming a self-assembled cubic nano-gold array on the surface of a silicon wafer, finally, putting the silicon wafer into an ethanol solution containing functional monomers, and adding 100 mu L of catalyst, standing and reacting for 11-13 h to prepare the cubic nanogold self-assembled array with amino groups on the surface of the silicon wafer, wherein the array has a function of detecting the TNT SERS probe.
In summary, the invention is the SERS probe which takes the cubic nano-gold single-layer self-assembly structure as the substrate on the silicon chip with the surface modified with the functional group, and the TNT detection is realized.
One is as follows: the polished silicon wafer is easy to oxidize to generate silicon dioxide, and the 3-mercaptopropyl triethoxysilane is hydrolyzed to modify the mercaptopropyl group of a functional group on the surface of the silicon wafer, so that the gold nanoparticles can be self-assembled on the surface of the silicon wafer in a single layer.
The second step is as follows: meanwhile, 3-aminopropyltriethoxysilane is hydrolyzed to modify an aminopropyl group rich in an electronic functional group on the surface of a silicon wafer, and the aminopropyl group and three electron-deficient nitro groups in TNT molecules are subjected to electrostatic interaction to realize high-selectivity recognition of TNT, so that the TNT molecules are adhered to the surface of a single-layer square nanogold, and the conventional Raman signals of the TNT molecules are enhanced by utilizing a local surface plasmon resonance field on the metal surface to realize high-sensitivity detection of trace TNT.
And thirdly: the cubic nanogold has an excellent SERS effect, and the SERS probe on the silicon wafer has the advantages of low cost, convenience in operation and the like.
Fourthly, the method comprises the following steps: the silicon chip modified with sulfydryl enables the nano-gold to be self-assembled on the surface of the silicon chip to form an array, and SERS signals are conveniently formed.
Drawings
FIG. 1 is a schematic diagram of the preparation of a cubic nanogold SERS probe for TNT detection according to the invention.
FIG. 2 shows the prepared seed gold nanoparticle sols of different particle sizes.
FIG. 3 shows cubic nanogold sol with different particle sizes prepared by the invention.
FIG. 4 is the ultraviolet-visible spectrum of the seed gold sol prepared by the present invention.
FIG. 5 is a cubic nanogold SEM prepared according to the invention.
FIG. 6 is the ultraviolet-visible spectrum of cubic nanogold prepared by the invention.
FIG. 7 is a Raman spectrum of TNT not placed on a cubic nanogold SERS probe prepared according to the invention.
FIG. 8 is a Raman spectrum of TNT placed on a cubic nanogold SERS probe prepared according to the invention.
FIG. 9 shows a silicon wafer (A) used in the present invention and a cubic nanogold SERS probe (B) prepared from the silicon wafer.
The embodiments are further explained with reference to the drawings
FIG. 1 is a schematic diagram of the preparation of a cubic nanogold SERS probe for TNT detection according to the invention. Firstly, 1 multiplied by 1cm is ground by 3000-mesh sand paper2The silicon wafer is ultrasonically washed by concentrated sulfuric acid-hydrogen peroxide mixed solution, acetone and deionized water in a volume ratio of 1:4 respectively, then placed for 2 weeks to slowly oxidize the surface of the silicon wafer and to be rich in hydroxyl, the polished surface of the silicon wafer is placed upwards into ethanol solution containing an adhesive, then a catalyst is added, standing reaction is carried out for 12 hours, molecules of the adhesive and the surface of the silicon wafer form strong hydrogen bond action due to hydrolysis of siloxane at one end of the adhesive and are adhered to the surface of the silicon wafer, then the silicon wafer is taken out, is repeatedly washed by absolute ethyl alcohol and then is naturally dried in the air, the polished surface of the silicon wafer is placed upwards into cubic nano-gold sol solution and is placed for about 6 hours to ensure that sulfydryl at the other end of the adhesive and metal gold form stable S-Au bonds, a self-assembled nano-gold array is formed on the surface of the silicon wafer, finally, the silicon wafer is placed, standing and reacting for 12h, preparing a cubic nano-gold self-assembly array with amino on the surface of the silicon wafer, wherein when TNT is added, the electron-rich amino on the surface of the silicon wafer interacts with three electron-deficient nitro groups in TNT molecules through electrostatic interaction, so that the TNT molecules are adhered to the surfaces of cubic nano-gold particles, and the conventional Raman signals of the TNT molecules are amplified and enhanced by utilizing a local surface plasmon resonance field on the surface of metal, so that the TNT is detected.
FIG. 2 shows the prepared seed gold nanoparticle sols of different particle sizes. Respectively adding HAuCl with the mass concentration of 0.05 percent4Adding 1mL, 5mL, 10mL and 15mL of the solution into a flask containing 50mL of the aqueous solution, placing the flask in a constant-temperature oil bath with a reflux device, magnetically stirring at 500 rpm, heating to 160 ℃, adding 4mL of a reducing agent, and continuing to heat for 15min under the same conditions with HAuCl4The amount is increased, the color of the prepared seed crystal gold is gradually deepened, which shows that the particle size is continuously increased, and thus, the seed crystal gold sol with different particle sizes is obtained.
FIG. 3 is a cross-sectional view of a film prepared by the present inventionCubic nanogold sol with the same grain diameter. In a 50mL three-neck flask, the HAuCl with the mass fraction of 0.05 percent is added4Solution 1mL and 0.04 mol. L-1NH of (2)21.0mL of OH & HCl solution is evenly shaken at 300r/min for 8min in a reciprocating oscillator, the mixed solution is diluted to 10mL by a stabilizing agent, the solution is fully mixed by continuously shaking for 10min, then reducing agent (0, 0.2, 0.4, 0.6, 0.8, 1 mL) solutions are respectively injected, then 100 muL of synthesized seed gold sol is injected by a microsyringe with the dosage range of 100-1000 muL, shaking reaction is carried out at room temperature for 4h at 250r/min, 2mL of the reaction mixture is placed in a 15mL centrifuge tube, after centrifugal separation at 8000rpm for 10min, supernatant is removed, the steps are repeated for 5 times in order to increase the concentration of gold particles in the 15mL centrifuge tube, and the obtained deposited sol is re-dispersed in a volume ratio of 1: 1, 10mL of ethanol and water to prepare the cubic nanogold sol. In the figure, deionized water and 0, 0.2, 0.4, 0.6, 0.8 and 1ml of NO are added from left to right in sequence3The gold sol generated by the reaction of the solution changes from colorless to blue to bluish-purple and finally is light brown.
FIG. 4 is the ultraviolet-visible spectrum of the seed gold sol prepared by the present invention. Respectively taken from 0.05% HAuCl43mL of seed gold sol prepared from 1mL, 5mL, 10mL and 15mL of solution is placed in a cuvette, and the absorption intensity of different samples can be obviously enhanced in the ultraviolet visible spectrum, which indicates that the concentration of the seed gold sol formed by the seed gold sol is gradually increased, namely the diameter of the small-particle gold nano-seed is gradually increased.
FIG. 5 is a cubic nanogold SEM prepared according to the invention. The cubic nanogold is regular in shape and good in dispersion effect, and lays a foundation for further preparing the cubic nanogold SERS probe.
FIG. 6 is the ultraviolet-visible spectrum of cubic nanogold prepared by the invention. 0.2mL, 0.4mL, 0.6mL, 0.8mL and 1mL of reducing agent are respectively added into the seed crystal gold sol to obtain the cubic nanogold, and the red shift phenomenon of the absorption intensity of different samples can be seen in the ultraviolet visible spectrum of the cubic nanogold, which indicates that the three-dimensional size of the cubic nanogold formed by the cubic nanogold is gradually increased.
FIG. 7 is a Raman spectrum of TNT not placed on a cubic nanogold SERS probe prepared according to the invention. Firstly, ethanol and acetonitrile with the volume ratio of 4:1 are respectively used as solvents to prepare the concentration of 10-9-10-4molL-120uL of the TNT solution is respectively dripped on a blank silicon chip, and the main three absorption peak positions in a Raman spectrum are respectively 562, 790 and 1094 cm-1The intensity was 102, 30, 145, 20, respectively, and the concentration of TNT from bottom to top was 10, respectively-9-10-4molL-1The TNT raman peak is relatively weak.
FIG. 8 is a Raman spectrum of TNT placed on a cubic nanogold SERS probe prepared according to the invention. Firstly, ethanol and acetonitrile with the volume ratio of 4:1 are respectively used as solvents to prepare the concentration of 10-9-10-4molL-1Respectively dropping 20uL of the TNT solution on a silicon chip of a cubic nanogold SERS probe, wherein four main absorption peak positions in a Raman spectrum are respectively 238 cm, 1371 cm, 1585 cm and 2932 cm-1Raman intensities 14147, 13545, 21238, 3592, and TNT concentrations from bottom to top 10-9-10-4molL-1Compared with the graph of fig. 7, the cubic nanogold SERS probe has an obvious enhancement effect on the Raman peak optical signal of the TNT, so that the trace TNT can be detected.
FIG. 9 shows a silicon wafer (A) used in the present invention and a cubic nanogold SERS probe (B) prepared from the silicon wafer. First, a circular silicon wafer having a diameter of 150mm was cut to obtain 1X 1cm2The silicon wafer was polished with 3000 mesh sandpaper (1X 1 cm) as shown in FIG. 9 (A)2Ultrasonically washing a silicon wafer for 4-6 min by using concentrated sulfuric acid-hydrogen peroxide mixed solution, acetone and deionized water in a volume ratio of 1:4 respectively, standing for 1-3 weeks, slowly oxidizing the surface of the silicon wafer, putting the polished surface of the silicon wafer upwards into ethanol solution containing a binder, adding 100 mu L of catalyst, standing for reaction for 11-13 h, taking out the silicon wafer, repeatedly washing the silicon wafer with absolute ethyl alcohol, naturally drying the silicon wafer in the air, putting the polished surface of the silicon wafer upwards into cubic nanogold sol solution, standing for 5-7 h to form a self-assembled nanogold array on the surface of the silicon wafer, and finally, adding a nano gold sol into the silicon wafer, and finally, adding a solvent to the silicon waferAnd then putting the silicon wafer into an ethanol solution containing a functional monomer, adding 100 mu L of a catalyst, standing and reacting for 11-13 h to prepare a cubic nanogold self-assembled array with amino groups on the surface of the silicon wafer, wherein the cubic nanogold SERS probe is used for detecting TNT (trinitrotoluene), and is shown in a figure 9 (B).
Detailed Description
A preparation method of a cubic nanogold SERS probe for TNT detection is characterized by comprising the following steps: the SERS probe is self-assembled on a silicon chip with a surface modified sulfydryl through cubic gold nanoparticles, electron-rich amino on the surface of the silicon chip and three electron-poor nitro groups in TNT molecules are subjected to electrostatic interaction, so that the TNT molecules are adhered to the surfaces of the cubic gold nanoparticles, and the conventional Raman signals of the TNT molecules are amplified and enhanced by utilizing a local surface plasmon resonance field of the cubic gold nanoparticles, so that the TNT is detected, wherein the preparation process of the SERS probe comprises the following three steps:
the first step is the preparation of seed gold sol: firstly, measuring 1-15 mL of HAuCl4Adding the solution into a 250mL three-neck flask containing 50mL deionized water, then placing the solution into a constant-temperature oil bath tank with a reflux device, magnetically stirring at the rotation speed of 400-600 rpm, heating to the temperature of 150-170 ℃, then adding 3-5 mL of a reducing agent A, changing the color of the reaction mixed solution from light yellow to orange, finally changing to wine red, stopping heating and stirring, cooling to room temperature, standing in a dark place, and storing in a refrigerator;
the second step is the preparation of cubic nano-gold particles: firstly, measuring 0.2-1.0 mL HAuCl4Placing the solution and 0.2-1.0 mL of reducing agent B in a 50mL three-mouth beaker, placing the three-mouth beaker in a reciprocating oscillator, oscillating for 5-10 min at the rotation speed of 250-350 rpm, then diluting the mixed solution to 10mL by using a stabilizing agent, continuing oscillating for 9-11 min to fully mix the mixed solution, then adding 0.2-1 mL of reducing agent C into the mixed solution, then injecting 100 mu L of the seed gold sol synthesized in the first step into a micro-injector with the dosage range of 100-1000 mu L, then oscillating for 2-6 h at the room temperature of 240-260 rpm, taking 2mL of the reaction mixture, placing the reaction mixture in a 15mL centrifuge tubeAnd after centrifugal separation at 7000-9000 rpm for 10min, removing the supernatant, repeating the steps for 5 times to increase the concentration of gold particles in the gold sol in a 15mL centrifugal tube, and re-dispersing the obtained deposited sol in a solvent with a volume ratio of 1: 1, preparing a mixed solution of 10mL of ethanol and water to obtain cubic nano gold sol;
the third step is the preparation of a cubic nanogold SERS probe: first, 1X 1cm was sanded with 3000 mesh sandpaper2Ultrasonically washing a silicon wafer for 4-6 min by using concentrated sulfuric acid-hydrogen peroxide mixed solution, acetone and deionized water in a volume ratio of 1:4 respectively, standing for 1-3 weeks, slowly oxidizing the surface of the silicon wafer, putting the polished surface of the silicon wafer upwards into ethanol solution containing a binder, adding 100 mu L of catalyst, standing for reaction for 11-13 h, then taking out the silicon wafer, repeatedly washing the silicon wafer with absolute ethyl alcohol, naturally drying the silicon wafer, putting the polished surface of the silicon wafer upwards into a cubic nano-gold sol solution, standing for about 5-7 hours, forming self-assembled nano gold array on the surface of the silicon chip, finally placing the silicon chip into ethanol solution containing functional monomers, and adding 100 mu L of catalyst, standing and reacting for 11-13 h to prepare the cubic nanogold self-assembled array with amino groups on the surface of the silicon wafer, wherein the array has a function of detecting the TNT SERS probe.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
Firstly, preparing gold sol and cubic nano gold particles, and secondly, grinding the 1 multiplied by 1cm2The surface of a silicon chip is firstly modified with sulfydryl, then a cubic nano-gold monolayer is self-assembled on the surface of the silicon chip, finally, amino is modified on the surface of the silicon chip, electron-rich amino and three electron-deficient nitro groups in TNT molecules are subjected to electrostatic interaction, so that the TNT molecules are adhered to the surfaces of the cubic nano-gold particles, and the conventional Raman signals of the TNT molecules are amplified and enhanced by utilizing the local surface plasmon resonance field of the cubic nano-gold particles, so that the TNT detection is realized, wherein the preparation process of the SERS probe comprises the following three steps:
the first step is the preparation of seed gold sol: first, 8mL of HAuCl was measured4The solution was added to a 250mL three-necked flask containing 50mL of deionized water, which was then placed in a constant flow apparatusIn a warm oil bath tank, performing magnetic stirring at the rotation speed of 500 rpm, heating to 160 ℃, then adding 4mL of a reducing agent A, changing the color of a reaction mixed solution from light yellow to orange, finally changing to wine red, stopping heating and stirring, cooling to room temperature, standing and storing in a refrigerator in a dark place;
the second step is the preparation of cubic nano-gold particles: first, 1.0mL of HAuCl was measured4Placing the solution and 1.0mL of reducing agent B in a 50mL three-mouth beaker, placing the three-mouth flask in a reciprocating oscillator, oscillating for 8min at the rotating speed of 300rpm, then diluting the mixed solution to 10mL by using a stabilizing agent, continuing oscillating for 10min to fully mix the mixed solution, then adding 1mL of reducing agent C into the mixed solution, then injecting 100 mu L of the seed crystal gold sol synthesized in the first step by using a microsyringe with the range of 100-1000 mu L, then oscillating for reaction for 4h at the room temperature of 250rpm, placing 2mL of the reaction mixture in a 15mL centrifuge tube, centrifuging for 10min at 8000rpm, removing supernatant, repeating the steps for 5 times to improve the concentration of gold particles in the 15mL centrifuge tube, and then re-dispersing the obtained deposited sol in a volume ratio of 1: 1, preparing a mixed solution of 10mL of ethanol and water to obtain cubic nano gold sol;
the third step is the preparation of a cubic nanogold SERS probe: first, 1X 1cm was sanded with 3000 mesh sandpaper2The method comprises the following steps of ultrasonically washing a silicon wafer for 5min by concentrated sulfuric acid-hydrogen peroxide mixed solution, acetone and deionized water in a volume ratio of 1:4, placing the silicon wafer for 2 weeks, slowly oxidizing the surface of the silicon wafer, placing the polished surface of the silicon wafer upwards into ethanol solution containing an adhesive, adding 100 mu L of catalyst, standing for reaction for 12 hours, taking the silicon wafer out, repeatedly washing the silicon wafer by absolute ethyl alcohol, naturally drying the silicon wafer in the air, placing the polished surface of the silicon wafer upwards into cubic nanogold sol solution, standing for about 6 hours to form a self-assembled nanogold array on the surface of the silicon wafer, finally placing the silicon wafer into ethanol solution containing a functional monomer, adding 100 mu L of catalyst, standing for reaction for 12 hours to prepare the cubic nanogold self-assembled array with amino on the surface of the silicon wafer, wherein the SERS probe has a function of detecting TNT.

Claims (3)

1. A preparation method of a cubic nanogold SERS probe for TNT detection is characterized by comprising the following steps: the cubic nanogold SERS probe is formed by self-assembling cubic nanogold particles on a silicon chip with surface modified sulfydryl, electron-rich amino on the surface of the silicon chip and three electron-poor nitro groups in TNT molecules are subjected to electrostatic interaction, so that the TNT molecules are adhered to the surfaces of the cubic nanogold particles, and the conventional Raman signals of the TNT molecules are amplified and enhanced by utilizing a local surface plasmon resonance field of the cubic nanogold particles, so that the TNT is detected, wherein the preparation method comprises the following three steps:
1.1 the first step is the preparation of seed gold sol: firstly, measuring 1-15 mL of HAuCl4Adding the solution into a 250mL three-neck flask containing 50mL deionized water, then placing the three-neck flask into a constant-temperature oil bath tank with a reflux device, magnetically stirring at the rotating speed of 400-600 rpm, heating to the temperature of 150-170 ℃, then adding 3-5 mL sodium citrate, changing the color of the reaction mixed solution from light yellow to orange, finally changing to wine red, stopping heating and stirring, cooling to room temperature, standing in a dark place, and storing in a refrigerator;
1.2 the second step is the preparation of cubic gold nanoparticles: firstly, measuring 0.2-1.0 mL HAuCl4Placing the solution and 0.2-1.0 mL hydroxylamine hydrochloride into a 50mL three-mouth beaker, placing the three-mouth flask into a reciprocating oscillator, oscillating for 5-10 min at the rotation speed of 250-350 rpm, then diluting the mixed solution to 10mL by using 20% polyethylene glycol 2000 aqueous solution, continuing oscillating for 9-11 min to fully mix the mixed solution, then adding 0.2-1 mL silver nitrate into the mixed solution, then injecting 100 muL of the seed gold sol synthesized in the first step by using a trace amount range of 100-1000 muL, then oscillating for 2-6 h at the room temperature of 240-260 rpm, placing 2mL of the reaction mixture into a 15mL centrifuge tube, centrifuging for 10min at 7000-9000 rpm, removing supernatant, and in order to improve the concentration of the gold particles in the 15mL centrifuge tube, repeating the steps of taking the reaction mixture, centrifuging and removing the supernatant for 5 times to obtainAnd redispersing the deposited sol in a solvent having a volume ratio of 1: 1, preparing a mixed solution of 10mL of ethanol and water to obtain cubic nano gold sol;
1.3 the third step is the preparation of a cubic nanogold SERS probe: first, 1X 1cm was sanded with 3000 mesh sandpaper2Ultrasonically washing a silicon wafer for 4-6 min by using concentrated sulfuric acid-hydrogen peroxide mixed solution, acetone and deionized water in a volume ratio of 1:4 respectively, standing for 1-3 weeks, slowly oxidizing the surface of the silicon wafer, putting the polished surface of the silicon wafer upwards into ethanol solution containing 3-mercaptopropyltriethoxysilane, adding 100 mu L of ammonia water with the mass concentration of 25%, standing for reaction for 11-13 h, taking out the silicon wafer, repeatedly washing the silicon wafer with absolute ethyl alcohol, naturally drying in the air, putting the polished surface upwards into cubic nanogold sol solution, standing for 5-7 h to form a self-assembled nanogold array on the surface of the silicon wafer, finally putting the silicon wafer into ethanol solution containing 3-aminopropyltriethoxysilane, adding 100 mu L of ammonia water with the mass concentration of 25%, standing for reaction for 11-13 h to prepare the cubic nanogold self-assembled array with amino groups on the surface of the silicon wafer, the SERS probe has a function of detecting TNT.
2. The method for preparing the cubic nanogold SERS probe for TNT detection as claimed in claim 1, wherein the method comprises the following steps: the size of the cubic gold nanoparticles is controlled by the amount of reactants and the reaction time.
3. The method for preparing the cubic nanogold SERS probe for TNT detection as claimed in claim 1, wherein the method comprises the following steps: the self-assembled array in the preparation of the cubic nanogold SERS probe is single-layer cubic nanogold with a space structure.
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